Kaplan U.S. Pat. No. 4,438,130 discloses some 1-oxa-, aza- and thia-spirocyclic compounds which are useful as analgesics. That patent also refers to other prior patents which may be of interest to the reader hereof.
Those skilled in the art continue to search for new and more potent or otherwise advantageous chemical compounds which have activity as analgesic drug compounds or for other pharmaceutical use or chemical intermediate purposes.